Teletypewriter switching system



April 1944- R. J. ANSPACH 2,345,912

TELETYPEW'RITER SWITCHING SYSTEM Filed Sept. 6, 1941 INVENTOR fispac/a ATTORNEY Patented Apr. 4, 1944 TELETYPEWRITER SWITCHING SYSTEM Russell Jacob Anspach, Westfield, N. J., assignor to American Telephone and Telegraph Company, a corporation of New York Application September 6, 1941, Serial N0. 409,768

7 Claims.

This invention relates to telegraph and teletypewriter systems and more particularly to round robin systems for telegraph or teletypewriter circuits and apparatus.

There are at present several type of so-called round robin systems in use in which a plurality of teletypewriter stations are interconnected in the form of a ring or loop in such a way that messages may be transmitted from any one of the stations in the system to all of the other stations so that all of the stations, including the station transmitting the messages, may receive the messages and prepare copies of the messages. In the usual round robin system two paths are provided to connect each station into the round robin system, one of the paths being employed for transmitting from the station into the rest of the round robin system and the other path for receiving messages from the other stations. Local copy is obtained after transmission of the messages around the ring or loop of the system. In many cases some stations may be in locations where line facilities are limited, and considerable construction might be required to provide separate sending and receiving legs to such stations to include such stations in the round robin systems. In such cases it would be advantageous to operate these legs in such a manner that sending and receiving operations, together with cutting and uncutting operations to connect or disconnect the remote stations into the round robin system, could be done over a single line conductor instead of over two conductors as has been the prior practice.

In accordance with this invention there is provided a novel form of round robin system for teletypewriter or like apparatus, the round robin system including one or more outlying point at which teletypewriter apparatus may be located. In the arrangement to be described hereinafter the outlying point to be specifically considered may be connected by a single telegraph channel to the central office which is connected to the round robin system. Arrangements are provided for permitting the operator at the outlying polnt to cut" his teletypewriter apparatus into or out of the round robin system as desired, and at the same time allow the operator at the outlying point to obtain a copy of his own messages. Thus in the arrangement contemplated the apparatus at the outlying point will receive a copy of all messages transmitted over the round robin system in the usual manner, but after a "cut" is instituted at the outlying point, the operator at the outlying point may send messages into the round robin system and home copy of the messages emanating from the outlying point will be received over a local circuit.

Thi invention will be better understood from the detailed description hereinafter following when read in connection with the accompanying drawing showing one embodiment of the invention merely for the purpose of illustration.

Referring to the drawing, there is shown a round robin system for teletypewriter apparatus, the system interconnecting a plurality of stations designated STAI, STA: and STA; and another station which may include a central office C0 and an outlying station or point OP which is connected to the central offlce by a single line conductor E. As is well known, messages emanating from any one of the stations, such as STAI, will be transmitted to all of the other stations including the central office CO and its connecting station OP, so that copies of the messages may be prepared at each of the various stations and at the outlying point OP. The outlying point 0P may include a break relay A, a receiving relay B, the armature of which is connected to a teletypewriter TI'Y, a sending relay S and a key L for cutting the sending apparatus at the outlying point into or out of the round robin system, as will be described more fully hereinafter. The apparatus at the central oflice CO may include a relay V, one of the windings V1 of which is always connected to the round robin system; a relay P which is normal ly unoperated but becomes operated only when the key L at the outlying point OP is manipulated to "cut" the sending apparatus of the outlying point OP into the round robin system, the relay P being released when the key L is returned to its uncut" position; a relay W having its main winding W1 in series with the line E which extends between the outlying point OP and the central oflice CO, as well as other relays to be subsequently described.

When messages are transmitted over the round robin system from any one of the stations STA1, STA: or STAs, the currents flowing through the winding V1 of the relay V will move its armature between its contacts M and S to connect oppositely poled batteries to the line E over a circuit which includes the armature of relay V. the armature P1 of relay P and its back contact, the noise killer and potentiometer N1, the breakafter-make contact of armature P5 of relay P, the winding W1 of relay W and the resistor Z1. The line E is connected to ground at the contact of swinger Li of the key L at the outlying point OP,

the interconnected circuit including the lower swinger L2 and contact of the key L and the winding B1 of relay B. oppositely directed currents corresponding to the oppositely poled voltages supplied to the contacts of the armature of relay V will traverse the winding B1 of relay B and the armature of relay B will be moved between its marking and spacing contacts M and S to operate the teletypewriter 'I'IY in accordance with the received signals. Thus the teletypewriter 'I'I'Y will prepare a record of all messages passed over the round robin system.

When the operator at the outlying point OP desires to interrupt the transmission from the other stations so that he may transmit messages over the round robin system, he will operat the key L by moving it to the left. The upper swinger L1 of the key L will then be disconnected from ground and instead connected to positive battery over a circuit which includes another noise killer and potentiometer N2 and the armature and contact M of the relay S. At the same time the short-circuit around the winding A1 of relay A will be opened at the lower swinger L2 of the key L. Thus the line E will be connected at the outlying point OP to the positive battery. At the central oflice CO the line E will be connected to negative battery connected to the marking contact M of the relay V. The increased current over the line E which follows the operation of the key L will cause the armature of the relay A to move to its spacing contact S. This in turn will cause the negative battery connected to the spacing contact S of relay A to be connected through a resistor Z2 to the lower windin B2 of relay B, and hence the armature of relay B will move to its spacing contact S. When this happens, the teletypewriter 'I'IY will be opencircuited at the contact S of relay B, and the teletypewriter will, therefore, run open."

The increased current over line E which results from the operation of the cutting key L also causes relay W at the central ofilce CO to operate so as to move its armature to its marking contact M. Relay P will then operate, current flowing from positive battery connected to resistor Z4, through the winding of relay P, the break-after-make contact of armature P2 of relay P, th armature and contact M of relay W and the negative battery connected thereto. Immediately after relay P operates, it becomes locked in its operated condition over a circuit which includes positive battery, resistor Z4, the winding of relay P, the armature P2 of relay P and its makebefore-break contact, the break-after-make contact of relay D2 and the negative battery connected to the make-before-break contact of relay D1. Thus the relay P becomes operated immediately after key L is closed and becomes locked immediately thereafter.

The operation of relay P grounds the line E at the central ofiice CO over a circuit which includes resistor Z1, the winding W1 of relay W, the make-before-break contact of armature P5 of relay P, armature P5, and the armature and back contact of relay Q. The operation of relay P at the same time opens the circuit of the biasing winding We of relay W at the back contact of armature P6 of relay P, this winding having formerly been connected to positive battery by way of resistor Z5 and the back contact and armature P6 of relay P. Moreover, the round robin system will be split at the break-after-make contacts of armatures Po and P1 of relay P to allow signaling currents to be transmitted from station GP to the round robin system, as will be described. The armature of relay W will be connected to the sending side of the round robin system over a circuit which includes the marking contact M and armature of relay W, the armature and contact M of relay Y, the resistor Za, the armature Po of relay P and its make-before-break contact. This permits the pulses transmitted to relay W from station OP over line E to be repeated into the round robin system, so that the signals corresponding to these pulses may be reproduced at the stations STAI, STA: and STAa.

The operation of relay P also causes the armature of the relay V to be connected to the slow-release relay Dz over a circuit which includes the armature P4 of relay P and its make contact, the make contact and armature P: of relay P, the winding of relay D2, the resistor Zn: and positive battery. This will enable any break signal received from any one of the stations STAl. S'I'Az or STA3 to cause the armature of relay V to close its spacing contact S and hence allow positive battery to be connected to opposite terminals of the winding of the slow-release relay Dz. so that in due course the relay D2 will be released The release of relay D will result in "opening" the circuit of the teletypewriter at TTY station OP to apprise the operator of the break signal, as will be subsequently described.

The now normal line current traversing line E causes the relay A at the outlying point OP to return to its marking contact M. This removes current from the bias winding B2 of relay B, thereby permitting relay B to return its armature to its marking contact M. When the marking contact M of relay B is closed, the teletypewriter TTY is then connected over a completed circuit through the armature of relay B and its marking contact M and, therefore, the teletypewriter T'I'Y will stop running open," thereby indicating that the cut has been fully effected.

After the "cut has been completed, the operator at the outlying point OP may then send signals over the round robin circuit, as will now be described. To transmit such signals the key K, which is in series with the W1 winding of relay S and a battery, may be operated. When the key K is closed, the current in the W1 winding of relay S will overpower the biasing current in winding W2 and the armature of relay S will be moved to its marking contact M, thereby applying positive battery to the line E over a circuit which includes the apparatus N2, the back contact and armature L1 of key L, the winding B1 of relay B and the winding A1 of relay A. The opening of key K will, on the other hand, cause the current in winding W1 to fall to zero and the armature of relay S will be positioned on its spacing contact S by the biasing current in winding W2, thereby connecting negative battery to the line E over the same circuit as already described. Thus the operation of key K will be employed to apply oppositely poled batteries to the line E to transmit one-way polar signals in the usual way over the line E to the central oflice G0, a positive battery being connected to line E for the marking condition and a negative battery for the spacing condition. These oppositely poled batteries will move the armature of relay W between its marking and spacing contacts M and S, and oppositely poled batteries will be connected to the sending side of the round robin system over a circuit controlled by the armature of relay W as already described. These oppositely poled batteries will convey the transmitted signals to the various stations of the round robin system in a well-known manner.

The operator at the outlying point OP may uncut his transmitting circuit from the line E by releasing the key L. This may be done by moving the key L to the right. This then grounds the line E at the swinger L1 of key L, and at the same time returns the short circuit around the winding A1 of relay A, which is completed by the lower swinger L: of key L. Thus the line E now becomes grounded at both ends and, therefore, no current flows thereover. The absence of voltage across the resistor Z1 which is in series with the line E removes current from the full wave rectifier R. bridging the resistor Z1, and hence no current flows through the upper windings of relays X and Y. The armatures of relays X and Y, therefore, move to their spacing contacts S. The closure of contact S of relay X by its armature results in the removal of current from the slow-release relay DI and relay D1 releases. The release of relay D1 opens the locking circuit for relay P, the locking circuit,

break contact of relay P, the winding of relay P,

resistor Z4 and positive battery. Relay P consequently releases. The armatures Po and P1 of relay P become restored to their former positions as shown in the drawing and the round robin system is then returned to its original coni dition. Relay P is so constructed that. in releasing, the armature and contact P6 of relay P will close before armature P2 makes with its normal contact. This insures that the armature of relay W will be on its S contact thus preventing the reoperation of relay P as would happen if relay W were on its M contact when the P2 armature of relay P made with its normal contact.

As already pointed out, a break signal received over the round robin system while the circuit at the outlying point OP is cut" into the round robin system, causes the relay D2 to release. The release of relay D2 opens the shunt around the winding of relay Q previously established by the break-after-make contacts of relay D2. The removal of this shunt from the winding of relay Q permits relay Q to operate, the operating circuit for relay Q including the negative battery connected to the break-after-make contact of relay D, the winding of relay Q, the armature P2 of relay P and its make-before-break contact, the winding of relay P, the resistor Z4 and the positive battery connected thereto. The operation of relay Q connects negative battery to the line E over a circuit which includes the negative battery connected to the make contact of the armature of relay Q, the armature P5 of relay P and its make-before-break contact, the winding W1 of relay W and resistor Z1. Due to the connection of oppositely poled batteries to the opposite terminals of line E whenever the armature of relay S closes its marking contact M, the increased line current will operate relay A, which will move its armature to its spacing contact S. This will then cause relay B to operate its armature to its spacing contact S, and the circuit to the teletypewriter TTY will then be opened and held open to indicate the break signal.

It will be observed that when signals are being transmitted from the outlying point OP by opill eration of key K, the home copy will be provided by the operation of relay B which repeats the signals to the teletypewriter TTY. The home copy thus will not be obtained from the round robin system, but rather from the local circuit at the outlying point OP.

It will be understood that any of the other stations of the round robin system may be like wise equipped with apparatus such as that shown at station CO and any outlying point may be provided with equipment similar to that shown at station OP, and thereby provide such outlying points with round robin service using only a single wire between the stations such as CO and OP.

It will be understood that the key K may be the usual sending contacts of a teletypewriter T'I'Y1 which is employed for sending messages to the stations of the round robin system. If desired, a single teletypewriter of well-known type may be substituted for the two teletypewriters TTY and TTY1 shown, the single teletypewriter being used both for sending and receiving messages.

While this invention has been shown and de scribed in certain particular embodiments merely for the purpose of illustration, it will be understood that the general principles of this invention may be applied to other and widely varied organizations without departing from the spirit of the invention and the scope of the appended claims.

What is claimed is:

1. In a teletypewriter system, the combination of a plurality of distant stations, a central ofiice connected in a complete unidirectional loop with said distant stations to comprise a round robin system, an outlying station, a single line conductor connecting the central oflice with the outlying station. a teletypewriter at the outlying station, means for receiving over the conductor ex tending to the teletypewriter of the outlying station all messages reaching the central ofiice, sending apparatus at the outlying station, a control relay, and means for operating said control relay for cutting said sending apparatus into said loop extending to said distant stations, said means including means for transmitting messages over said conductor through the central oifice to the distant stations.

2. The combination of a plurality of teletypewriter stations connected to each other in a unidirectional loop comprising a round robin system, an outlying station, a single wire line, a control relay, means for operating said control relay to connect said outlying station to the round robin system over said line, and means responsive to the operation of said control relay for receiving over said line connected to the outlying station the messages transmitted over the round robin system, transmitting apparatus at the outlying station, said latter means including means for cuting said transmitting apparatus into the round robin system for transmitting messages over said line, to the teletypewriter stations of the round robin system.

3. In a teletypewriter system, the combination of a plurality of stations connected to each other in a round robin system so that signals will always be transmitted in the same direction over the system, an outlying station having transmitmitting apparatus and receiving apparatus, a single line conductor for connecting said outlying station with said round robin system, a control relay, means for operating said control relay for interconnecting the receiving apparatus and the stations of the round robin system so that messages transmitted over the round robin system will be received by said receiving apparatus, means controlled by said control relay for cutting the transmitting apparatus of the outlying station into the round robin system so that messages may be transmitted from the outlying station over said line conductor to the various stations of the round robin system.

4. In a teletypewriter system, the combination of a plurality of teietypewriter stations connected to each other in a round robin system so that signals will always be transmitted in the same direction over the system, an outlying station, a control relay, and means responsive to the operation of said control means for including said outlying station in said round robin system, said means comprising a single line conductor interconnecting the outlying station with the round robin system, receiving means at the outlying station for receiving all messages trans mitted over the round robin system, transmitting apparatus at the outlying station, means for cutting said transmitting apparatus at the outlying station into the round robin system so that messages may be transmitted from said outlying station over the round robin system over the single line conductor extending from the outlying station to the round robin system, and means for operating said receiving means at the outlying station in accordance with the messages transmitted from the transmitting apparatus of said outlying station.

5. In a teletypewriter system, the combination of a plurality of stations connected to each other in around robin system so that signals will always be transmitted in the same direction over the system, a main station included in said round robin system, a control relay, an outlying station connected by a single wire conductor to the main station through the contacts of said control relay, transmitting apparatus and receiving apparatus at said outlying station, means for actuating said receiving apparatus at the outlying station in accordance with any mes sages transmitted over the round robin system, means for applying said transmitting apparatus to the round robin system so that messages may be transmitted over said single wire conductor to the main station and then over the round robin system, and means interconnecting the transmitting and receiving apparatus at the outlying station so that all messages transmitted from the outlying station may be recorded by said receiving apparaus at said outlying station.

6. In a teletypewriter system, the combination of a plurality of stations connected to each other in a round robin system so that signals will always be transmitted in the same direction over the system, a main station included in said round robin system, a control relay, an outlying station connected by a single wire conductor to the main station through the contacts of said control relay, transmitting apparatus and receiving apparatus at said outlying station, means for actuating said receiving apparatus at the outlying station in accordance with any messages transmitted over the round robin system, means for applying said transmitting apparatus to the round robin system so that messages may be transmitted over said single wire conductor to the main station and then over the round robin system, means interconnecting the transmitting and receiving apparatus at the outlying station so that all messages transmitted from the outlying station may be recorded by said receiving apparatus at said outlying station, and

means responsive to a break signal received from any one of the stations of the round robin system for indicating at the outlying station that a break signal has been received.

'7. In a signaling system, the combination of a plurality of telegraph stations connected to each other in a round robin system so that signals will always be transmitted in the same direction over the system, an outlying telegraph station having transmitting apparatus and receiving apparatus, a control relay for associating said outlying station with said round robin system, a single wire line connecting said outlying station to the round robin system through contacts of said control relay, means for operating said receiving apparatus in accordance with the signals transmitted over the round robin system, and means for cutting said transmitting apparatus into the round robin system for transmitting signals over said line to the telegraph stations of the round robin system.

RUSSELL JACOB ANSPACH. 

